In the semiconductor industry, the minimum feature sizes of microelectronic devices are approaching the deep sub-micron regime to meet the demand for faster, lower power microprocessors and digital circuits. The downscaling of CMOS devices imposes scaling constraints on the gate dielectric material. The thickness of the standard SiO2 gate dielectric oxide is approaching a level (˜10 angstroms (Å)) at which tunneling currents may significantly impact transistor performance. To increase device reliability and reduce electron leakage from the gate electrode to the transistor channel, semiconductor transistor technology is using high-k gate dielectric materials that allow increased physical thickness of the gate dielectric layer while maintaining an equivalent gate oxide thickness (EOT) of less than about 10 Å. The variable “k” refers to the dielectric constant of a material.
Integration of high-k materials into semiconductor microstructures can result in formation of an interfacial oxide (SiO2) layer due to oxidation of the Si substrate. The presence of an oxide interfacial layer lowers the overall dielectric constant of the microstructure, thereby reducing the advantage of using a high-k dielectric material instead of SiO2. To reduce the effect of an oxide interfacial layer on the overall dielectric constant of the microstructure, the oxide layer may need to be thin. Deposition of a high-k dielectric layer onto a Si substrate can result in uncontrolled growth of an oxide interfacial layer that is too thick for current semiconductor transistor technology.